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The invention contained herein entitled xe2x80x9cPersonal Watercraft Variable Inlet/Intake Gratexe2x80x9d pertains to improvements made in the design and manufacture of inlet grates located beneath the hull of said watercraft prior to the jet pump assembly or impeller (see FIGS. 3,4), to which water is directed by an intake or inlet channel in the underside of the hull of the watercraft. The purpose of the conventional inlet grate is to provide protection against foreign objects entering the jet propulsion system, which may cause severe damage to the jet pump and/or one of its components. Furthermore, inlet/intake grates also exist to increase or improve pump pressure/flow of water through the jet pump assembly thus dramatically improving performance and handling of the watercraft. Due to the widespread growth of the sport, jet watercraft recreation, enhancements in the design, and/or manufacture of after market inlet grates has become a highly competitive business. The introduction of xe2x80x9cvariablexe2x80x9d technology to the design/manufacture of inlet grates will provide a solution to many performance problems associated with personal watercraft marine vehicles.
Current technology is this area consists of improvements made to current watercraft manufacture inlet grates. Typically, stock inlet/intake grates consist of a main grate generally containing a single diagonal plate/scoop. Stock inlet grates provide reasonable performance in smooth water conditions, however they lend themselves to problems of cavitation due to the inability to provide consistent pump pressure (flow to the pump or impeller) in cornering and in rough water conditions. Stangeland, U.S. Pat. No. 4,373,919 discloses an adjustable angle top loading plate, which is pivotally connected to the hull of a vessel. By the use of mechanical/electronic means and/or sensors, which measure the engine performance or speed of the watercraft, it succeeds in splitting the flow of water into upper and lower portions while varying the inlet area. However, this requires extensive, unnecessary alterations to the water craft and employment of unusual manufacturing techniques and is not easily adaptable to various watercraft as is the invention contained herein. Furthermore, the prior art fails to provide consistent pump pressure in cornering due to side support members. The prior art provides an equality of upper and lower portions but fails to provide a substantial increase in pump pressure as needed for increased torque and acceleration. Finally, the Strangeland design lends itself to dramatic increases in drag which causes a significant decrease in top speed performance. Tyler et al, U.S. Pat. No. 4,775,341 discloses a water directing apparatus which was provided for use on what is commonly referred to as a wetbike. Unlike personal watercraft currently produced, it contained a combination of skis rather than a hull common to most current marine vehicles. However, Tyler et al disclosed a series of laterally spaced fins which are positioned at various angles of attack, thus providing an upper and lower stream of water to the jet pump assembly. The patent disclosed by Tyler et al has led to the typical design of stock and after market intake grates currently on the market provided for modern personal watercraft vehicles. Tyler et al however, also discloses a second embodiment containing a lateral vane, which is pivotally connected to the inlet channel of the watercraft. This vane allegedly responded to increased pressure as a result of increasing speed. Although, the principle is similar to that contained herein, specific problems must have been obvious. This vane being pivotally connected to the inlet channel, similar to that disclosed by Strangeland as mentioned above, would effectively vary pump pressure with watercraft speed but would fail to provide full saturation of the impeller housing which leads to a loss of top speed performance. Furthermore, this device fails to offer protection of foreign objects from entering the inlet channel, which could lead to damage to pump components, and more importantly, serious injury to the rider could occur. Moyle et al U.S. Pat. No. 5,114,368 discloses a shaft shielding top loader which effectively divides the flow into upper and lower portions but is accomplished by a fixed top loading plate. It succeeds in providing improved acceleration and pump pressure, but provides a decrease in top end performance. Due to its inability to make necessary adjustments in pitch/angle to vary pump pressure as operating conditions require, it provides increased drag/turbulence and fails to provide a smooth flow which greatly reduces top end performance. It is a combination of some of these principles of the prior art, that lead to the improvement in inlet/intake grates, provided for use on modern personal watercraft containing a hull, that is contained herein.
The introduction of variable technology to the design/manufacture of inlet/intake grates will dramatically increase overall performance and handling of the watercraft and will be easily adaptable to various type/models thereof. Furthermore, it will provide a solution to the problems associated with the prior art as mentioned above. Variable inlet grates will increase pump pressure and improve overall performance by consistently providing a smooth flow of water through the pump assembly under all conditions. Under acceleration, when increased pump pressure is necessary, the variable inlet grate will provide an increase in water flow to the pump assembly thus increasing torque, which will dramatically improve low and mid range acceleration. As the watercraft begins to reach top speed, the variable intake grate will utilize the natural effects of hydrodynamics to make necessary adjustments in pitch to maintain a smooth flow while minimizing cavitation and fully saturating the lower impeller housing. The result is improved overall performance and handling without sacrificing top end performance. The introduction of variable technology to the design of personal watercraft inlet grates, will provide results which could never be achieved through current fixed intake grates currently on the market. Current intake grates succeed in providing improved performance in some areas, but fail to improve overall performance in both low and mid range acceleration as well as provide superior handling at all speeds without sacrificing top end performance.